V4L/DVB: ir-core: Remove warining noise if decoders compiled builtin

drivers/media/IR/ir-raw-event.c:55: warning: ‘wq_load’ defined but not used
drivers/media/IR/ir-raw-event.c:222: warning: ‘init_decoders’ defined but not used
drivers/media/IR/rc-map.c: In function ‘get_rc_map’:
drivers/media/IR/rc-map.c:40: warning: unused variable ‘rc’

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>